Yes you can remove the broken bolt and replace it
I use a Dremel tool to flatten off the broken end then center punch followed by drilling the bolt out with a left hand drill bit.
If your god is pleased with you the left hand drill will be enough to undo the bolt .
Otherwise there are a million you tube videos on removing broken bolts
To me the threads look fine in that picture but looks like the hub or flange is what got broken. Also looks like the blade must have gotten loose because the pins for it seems to be sheered off. Not to say that there may be a broken bolt down a bit deeper in that hole that would have to be taken out as bertsmoble1 has said and does work. Most anything can be repaired with a little work and time. (But not always) Another thing did you hit something when this happened? If you did may have other problems, does the mower still run?
